Polycarbonate resins are prepared by condensation-polymerization of an aromatic diol such as bisphenol A with a carbonate precursor such as a phosgene and have excellent impact strength, dimensional stability, heat resistance and transparency. Thus, the polycarbonate resins have application in a wide range of uses, such as exterior materials of electrical and electronic products, automobile parts, building materials, and optical components.
Recently, in order to apply these polycarbonate resins to more various fields, many studies have been made to obtain desired physical properties by copolymerizing two or more aromatic diol compounds having different structures from each other and introducing units having different structures in a main chain of the polycarbonate.
Especially, studies for introducing a polysiloxane structure in a main chain of the polycarbonate have proceeded, but most of these technologies have disadvantages in that production costs are high, and flame retardancy and chemical resistance are deteriorated.
Given the above circumstances, the present inventors have found that a polycarbonate composition comprising a copolycarbonate comprising a specific siloxane structure and a branched polycarbonate comprising a branched repeating unit is capable of improving flame retardancy and chemical resistance while maintaining high impact strength and melt index. The present invention has been completed on the basis of such a finding.